Method and apparatus for handling roaming lists in a wireless communication system

ABSTRACT

Method and apparatus for updating roaming lists. An error handling message is provided when the roaming list protocols within the elements of a system are not compatible. A roaming list format identifier is provided to the remote user identifying the protocol version supported by the network. The roaming list format identifier acts to either request an old version of the protocol or request the current stored format at the remote user. In one embodiment, the old version is the Preferred Roaming List, and the new version is the Extended Preferred Roaming List.

BACKGROUND

[0001] 1. Field

[0002] The present invention relates generally to handling roaming listsin a wireless communication system, and more specifically to updating apreferred roaming list and to coordinating different protocol versionsbetween a wireless communication network and remote users.

[0003] 2. Background

[0004] Protocols are regulations that govern the transmission andreceipt of information across a data communications link. Protocols aredetailed in a set of standards that assures that different networkproducts can work together. Any product using a given protocol shouldwork with any other product using the same protocol. In a wirelesscommunication system, protocols define the various architectural layersof the system. As protocols and standards are revised, those systemcomponents using an older version of the protocols and standards maybecome incompatible with those having newer capabilities. A variety ofmethods are used to overcome such incompatibility, wherein each fix isspecific to a protocol and/or standard.

[0005] One area of incompatibility often occurs when protocols governingtraditionally voice-dominated communications are expanded to also governhigh data rate transmissions. For example, a remote user of one serviceprovider, the home provider, may have access to other service providers,the foreign provider, when outside the service area of the homeprovider. The process is called roaming, and is facilitated by the useof roaming lists maintained by the remote user. The roaming list isupdated by the service provider as the list changes, e.g., a newrelationship with another service provider. The format of the roaminglist as well as the format of the transmissions to update the roaminglist may be specified by protocols in a standard. The addition of highdata rate services, or other new services, may require changes in formatto the roaming list as well as changes in the method of updating theroaming list. Such revisions to the protocol may cause incompatibilitydifficulties between the network and remote users. When the protocolrevision of the remote user is different from that of the network, theaccuracy and availability of the roaming list to the remote user may bejeopardized.

[0006] There is, therefore, a need in the art for an efficient procedureto configure, maintain and update preferred roaming lists over differenttransmission protocol versions in a wireless communication system.

SUMMARY

[0007] Embodiments disclosed herein address the above stated needs byproviding a method and apparatus for updating roaming lists, wherein aroaming list format identifier is provided to the remote useridentifying the protocol version supported by the network. The roaminglist format identifier acts to either request an old version of theprotocol or request the current stored format at the remote user. In oneembodiment, the old version is the Preferred Roaming List, and the newversion is the Extended Preferred Roaming List. On receipt of theroaming list format identifier and a configuration request, a remoteuser receives the roaming list format identifier transmits an errormessage if the format identifier is not compatible with the protocolversion currently used by the remote user. Similarly, the remote usertransmits configuration information if the format identifier iscompatible with the protocol version used by the remote user. An errorhandling message is provided when the roaming list protocols within theelements of a system are not compatible. .

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a communication system.

[0009]FIGS. 2-5 are timing diagrams illustrating procedures to update apreferred roaming list for various configurations of the remote user andthe network.

[0010]FIG. 6 is a flow diagram of a method for updating a preferredroaming list.

[0011]FIG. 7 is a mobile station.

DETAILED DESCRIPTION

[0012] The word “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

[0013] Wireless communication systems are widely deployed to providevarious types of communication such as voice, data, and so on. Thesesystems may be based on code division multiple access (CDMA), timedivision multiple access (TDMA), or some other modulation techniques. ACDMA system provides certain advantages over other types of systems,including increased system capacity.

[0014] A CDMA system may be designed to support one or more CDMAstandards such as (1) the “TIA/EIA-95-B Mobile Station-Base StationCompatibility Standard for Dual-Mode Wideband Spread Spectrum CellularSystem” (the IS-95 standard), (2) the standard offered by a consortiumnamed “3rd Generation Partnership Project” (3GPP) and embodied in a setof documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offeredby a consortium named “3rd Generation Partnership Project 2” (3GPP2) andembodied in a set of documents including “C.S0002-A Physical LayerStandard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A UpperLayer (Layer 3) Signaling Standard for cdma2000 Spread SpectrumSystems,” and the “C.S0024 cdma2000 High Rate Packet Data Air InterfaceSpecification” (the cdma2000 standard), (4) the “TIA/EIA-IS-856 CDMA2000High Rate Packet Data Air Interface Specification” (the IS-856standard), and (5) some other standards.

[0015] Cellular communication system users commonly have a serviceagreement with a cellular provider. The system operated by a cellularprovider may cover a limited geographical area. When a user travelsoutside of this geographical area, service may be provided by anothersystem operator, under a roaming agreement. There is often more than oneservice provider in a particular region, so a user may have a choice asto which service provider to roam with. As cellular communicationsystems have proliferated, networks of cellular systems have beenorganized under common service providers, or with contractual agreementsbetween service providers. Roaming fees are minimized or eliminated whena user transfers between systems which are party to such agreements. Assuch, modern mobile stations often make use of Preferred Roaming Lists(PRLs), which contain information about the preferred systems forroaming and various parameters needed for communication therewith. PRLsmay be pre-programmed in a mobile station when service is initiated.Alternatively, PRLs can be programmed with over-the-air data transfers.Such programming is described in “TIA/EIA-683-B Over-the-Air ServiceProvisioning of Mobile Stations in Spread Spectrum Systems”, a standardcompatible with the above named wireless communication systems.

[0016]FIG. 1 is a diagram of a wireless communication system 100according to one embodiment that supports a number of users, and whichcan implement various aspects of the invention. System 100 may bedesigned to support one or more CDMA standards and/or designs (e.g., theW-CDMA standard, the IS-95 standard, the cdma2000 standard, the IS-856standard). For simplicity, system 100 is shown to include three basestations 104 in communication with two mobile stations 106. The basestation and its coverage area are often collectively referred to as a“cell”. In IS-95 systems, a cell may include one or more sectors. In theW-CDMA specification, each sector of a base station and the sector'scoverage area is referred to as a cell. As used herein, the term basestation can be used interchangeably with the term access point. The termmobile station can be used interchangeably with the terms user equipment(UE), subscriber unit, subscriber station, access terminal, remoteterminal, or other corresponding terms known in the art. The term mobilestation encompasses fixed wireless applications.

[0017] Depending on the CDMA system being implemented, each mobilestation 106 may communicate with one (or possibly more) base stations104 on the forward link at any given moment, and may communicate withone or more base stations on the reverse link depending on whether ornot the mobile station is in soft handoff. The forward link (i.e.,downlink) refers to transmission from the base station to the mobilestation, and the reverse link (i.e., uplink) refers to transmission fromthe mobile station to the base station. The word “exemplary” is usedexclusively herein to mean “serving as an example, instance, orillustration.” Any embodiment described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments.

[0018]FIGS. 2-5 illustrate roaming list updating for variousconfigurations. For these examples, the systems support the protocolsdetailed in IS-683-B, and may support newer versions of the protocols.For example, an Extended PRL is supported as a new version of the PRL.The Extended PRL includes information used for high data rate servicesin addition to the information supported by the PRL. The Extended PRL isexpandable for other communication systems.

[0019]FIG. 2 illustrates call processing wherein both the remote unit orMobile Station (MS) and the network, identified as Over-The-Air serviceprovisioning Function (OTAF), support an old version Preferred RoamingList (PRL). The OTAF is a network infrastructure element, such as a BaseStation (BS) or Base Station Controller (BSC). For clarity, the oldversion will be referred to as the “PRL,” while the new version will bereferred to as the “E-PRL.” Note that alternate embodiments mayimplement any of a variety of naming conventions to identify a previousversion from a later version of a roaming list. Similarly, alternateembodiments may implement more than two versions. In the scenario ofFIG. 2, the OTAF sends a protocol capability request to the MS. The MSresponds indicating support for the PRL. The OTAF then sends a SystemSelection for Preferred Roaming List (SSPR) configuration requestmessage. Accordingly, the SSPR configuration request includes a BLOCK_IDfield. The BLOCK_ID field is used to identify the parameter blockrequested in this message. In this case, the BLOCK_ID field is set tothe hexadecimal value 0x300 (or the binary value 0000000) requesting theconfiguration, i.e., dimensions, of the old version PRL. As the MS onlysupports the old version PRL, the MS responds with the configurationinformation of the PRL. The OTAF then determines if there is a need toupdate the PRL at the MS. If a need exists, then the OTAF downloads thenew information for storage in the MS.

[0020]FIG. 3 illustrates the scenario wherein the OTAF supports E-PRL,while the MS only supports PRL. In this scenario, the OTAF checks thecapability of the MS, and in response sends an SSPR configurationrequest with the BLOCK_ID field set to 0x00 corresponding to the PRL.Note that the OTAF is capable of handling both PRL and E-PRL, andtherefore, is able to interface with a MS capable of either. In thiscase, the MS is only able to support PRL; the OTAF asks for the PRLconfiguration. The MS responds, and processing continues as in FIG. 2.

[0021]FIG. 4 illustrates the scenario wherein the OTAF supports PRL,while the MS supports both PRL and E-PRL. In this scenario, when theOTAF requests capability information, the MS sends a responseidentifying support of both PRL and E-PRL. The OTAF cannot handle theE-PRL information. Note that while the MS is able to support both PRLand E-PRL, the MS is only able to support one at a time. The OTAF thenrequests configuration information. The MS sends the configurationinformation in response. If the SSPR Configuration Request Messagecontains the request for the Preferred Roaming List Dimension ParameterBlock (BLOCK_ID=‘00000000’) and if the mobile station supportsSSPR_P-REV greater than or equal to ‘00000011’ and stores preferredroaming list associated with SSPR_P_REV greater than or equal to‘00000011’, then, the mobile station shall set the RESULT_CODE in theSSPR Configuration Response Message to ‘00100011’, “Rejected—PRL formatmismatch.” The mobile station shall include the parameter block with theBLOCK_LEN field set to zero. In other words, if the OTAF supports onlythe old version, while the MS supports the new version and is currentlystoring the roaming list in the new format, then the MS sends an errormessage to the OTAF. If the current roaming list stored in the MS is inthe PRL format, the OTAF receives the PRL configuration information andresponds accordingly. If, however, the current roaming list in the MS isin the E-PRL format, the OTAF receives configuration information that itcannot process. To avoid such problems, in the present embodiment, theOTAF sends the SSPR configuration request with the BLOCK_ID equal to0x00, indicating that the OTAF desires to receive the PRL configurationinformation. In this way, if the MS stores the PRL format, then the PRLconfiguration is sent to the OTAF. Else, if the MS stores the E-PRLformat, the MS sends the SSPR configuration response with an error codeto the OTAF. At this point, the OTAF is informed of the compatibilityproblem, and determines a correction strategy that is implementationspecific.

[0022]FIG. 5 illustrates a final scenario wherein the OTAF and the MSboth support the new version E-PRL. The OTAF determines the capabilityof the MS and identifies the MS as supporting both PRL and E-PRL. Atthis point, the OTAF does not know which format is currently stored inthe MS. For example, while the MS supports E-PRL, the MS may havechanged from a service provider that only supports PRL. The currentformat of the roaming list in the MS may therefore be PRL or E-PRL. TheOTAF desires to update the E-PRL if available. The OTAF sets theBLOCK_ID field in the SSPR configuration request message to 0x02. Thisindicates to the MS that the OTAF desires SSPR configuration informationregarding the current format of the roaming list. The MS responds withthe configuration information stored in the MS, the PRL dimensions orE-PRL dimensions, based on the current format.

[0023] According to the exemplary embodiment, a MS supporting both thenew and old versions uses an extended memory storage area for storingthe roaming list. Either format may be stored in the extended memorystorage area. Table 1 provides the E-PRL dimensions parameter block asstored in the MS. The PARAM_DATA field of the Extended Preferred RoamingList Dimensions Parameter Block consists of the fields listed. TABLE 1Extended Preferred Roaming List Dimensions Parameter Block Field Length(bits) MAX_PR_LIST_SIZE 16 CUR_PR_LIST_SIZE 16 PR_LIST_ID 16CUR_SSPR_P_REV 8 SSPR_P_REV-specific fields variable If CUR_SSPR_P_REVis ‘00000001’ the SSPR_P_REV- specific fields also include the followingfields: RESERVED 1 NUM_ACQ_RECS 9 NUM_SYS_RECS 14 If CUR_SSPR_P_REV is‘00000011’ the SSPR_P_REV- specific fields also include the followingfields: NUM_ACQ_RECS 9 NUM_COMMON_SUBNET_RECS 9 NUM_EXT_SYS_RECS 14

[0024]FIG. 6 is a flow diagram illustrating a process for updatingroaming lists according to one embodiment. As illustrated, the process400 begins by the MS receiving a capability request message at step 402.The MS responds by sending the capability information at step 404. Atstep 406 the MS receives the configuration request message from theOTAF. The configuration request message includes a BLOCK_ID field. Basedon the value in the BLOCK_ID field, the MS determines the appropriateresponse, decision diamond 408. If the OTAF requests current informationas to which format the MS is currently using for the roaming list,processing continues to step 410. The MS sends back the configurationinformation of the current roaming list stored. If the BLOCK_ID requestsPRL configuration information and the MS do not support E-PRL, thenprocessing continues to step 416 to send the PRL configurationinformation to the OTAF. If the BLOCK_ID requests PRL configurationinformation and the MS do support E-PRL, then the MS determines in whichformat (PRL or E-PRL) the roaming list is currently stored. If the listis stored in PRL format, processing continues to step 416. Else if thelist is stored in E-PRL format, processing continues to step 418 to senda response message with error code to the OTAF.

[0025]FIG. 7 shows an embodiment of mobile unit 500. For clarity, only asubset of the components is shown. Signals are received at antenna 510,and delivered to receiver 520 where amplification, down-conversion,sampling, and demodulating takes place. Various techniques for receivingCDMA signals are known in the art. In addition, the principles of thepresent invention apply with equal force to wireless communicationsystems deploying air interfaces other than those based on CDMA.Receiver 520 is in communication with a central processing unit (CPU)530. CPU 530 may be a microprocessor or digital signal processor (DSP),or one of various processors known in the art. CPU 530 communicates withmemory 540, which is shown containing roaming list 560. The roaming list560 can be programmed via over-the-air programming in conjunction withantenna 510 and receiver 520, or the data for the roaming list may comein from other inputs to CPU 530 (not shown). CPU 530 is also connectedto transmitter 550, for transmitting messages, data, voice, etc., usingany of the techniques for transmission known in the art. Transmitter 550is connected to antenna 510, for transmission to a base station, such asbase station 104. Receiver 520 and transmitter 550, in conjunction withantenna 510, can be used to communicate with one or more systemsidentified in the roaming list 560 when the mobile station is roaming.The mobile unit 500 is a hybrid unit supporting both PRL and E-PRL. Thememory storage locations of the PRL 560 may be used to store the E-PRLinformation as well. Roaming list decision unit 570 receives a roaminglist format identifier, such as the information contained in theBLOCK_ID as discussed hereinabove. The roaming list decision unit 570then determines the appropriate response as detailed in the process ofFIG. 6. The roaming list decision unit 570 also controls roaming liststorage in roaming list 560. The roaming list decision unit 570 providesthe configuration information to the CPU 530 for transmission.

[0026] Those of skill in the art would understand that information andsignals may be represented using any of a variety of differenttechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles, or any combination thereof.

[0027] Those of skill would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

[0028] The various illustrative logical blocks, modules, and circuitsdescribed in connection with the embodiments disclosed herein may beimplemented or performed with a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

[0029] The steps of a method or algorithm described in connection withthe embodiments disclosed herein may be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

[0030] The previous description of the disclosed embodiments is providedto enable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for updating a roaming list in a mobilestation, the mobile station storing a roaming list in a first format,the method comprising: receiving a roaming list format identifier;transmitting an error message if the format identifier is not compatiblewith the first format; and transmitting configuration information of thefirst format if the format identifier is compatible with the firstformat.
 2. The method as in claim 1, wherein the configurationinformation includes the dimensions of the first format.
 3. The methodas in claim 1, wherein the mobile station supports multiple roaming listformats.
 4. The method as in claim 3, wherein the mobile stationsupports a Preferred Roaming List format and an Extended PreferredRoaming List format.
 5. The method as in claim 1, further comprising:receiving updates to the roaming list if the format identifier iscompatible with the first format.
 6. A method for updating a roaminglist, the method comprising: receiving protocol capability information;determining a roaming list format identifier based on the protocolcapability information; and transmitting a configuration requestincluding the roaming list format identifier.
 7. The method as in claim6, further comprising: in response to the configuration request,receiving configuration information; determining a roaming list formatfor roaming list updates based on the configuration information; andtransmitting roaming list updates in the roaming list format.
 8. Themethod as in claim 6, wherein the configuration request is a SystemSelection Preferred Roaming (SSPR) Configuration Request.
 9. The methodas in claim 6, wherein the roaming list format identifier is transmittedin the BLOCK_ID field.
 10. The method as in claim 6, wherein the roaminglist format identifier is a first value for a first version roaming listprotocol.
 11. The method as in claim 10, wherein the roaming list formatidentifier is a second value for a second version roaming list protocol.12. The method as in claim 7, wherein the roaming list format identifieris a second value for a second version roaming list protocol.
 13. Amobile station, the mobile station storing a roaming list in a firstformat, the mobile station comprising: means for receiving a roaminglist format identifier; means for transmitting an error message if theformat identifier is not compatible with the first format; and means fortransmitting configuration information of the first format if the formatidentifier is compatible with the first format.
 14. A wirelesscommunication infrastructure element, comprising: means for receivingprotocol capability information; means for determining a roaming listformat identifier based on the protocol capability information; andmeans for transmitting a configuration request including the roaminglist format identifier.
 15. An wireless communication apparatus,comprising: processing element; memory storage unit adapted for storinga roaming list; and roaming list decision unit coupled to the processingelement and the memory storage unit, the roaming list decision unitadapted to determine a format for storing the roaming list, and toinitiate transmission of an error message when the format is notcompatible with a network format identifier.